code: def gen_batch_of_noise(cls, amp):
      noise_audio = np.random.uniform(
          low=-amp,
          high=amp,
          size=(1, int(cls.sample_rate * cls.audio_len_sec)),
      )
      return np.tile(noise_audio, [cls.batch_size, 1])
  
imports: from unittest import mock
  from absl.testing import parameterized
  import ddsp
  from ddsp.test_util import gen_np_batched_sinusoids
  from ddsp.test_util import gen_np_sinusoid
  import ddsp.training.metrics
  import numpy
  import tensorflow.compat.v2
label_desc: Use image node_id 2 for calling the MetricsObjectsTest obj's underlying member method code with example usage: obj.gen_batch_of_noise(cls, amp) and returns: np